1. Field of the Invention
The present invention relates generally to a vehicle alternator and, more particularly, to a connection structure and a method of connecting field coils and lead wires in a vehicle alternator, in which an electrical connection structure between the lead wires of a slip ring and the field coils of a rotor assembly is achieved by performing epoxy curing in the space between hubs, which protrude from the front surface of a rear fan, and guide pockets, so that a work process is simplified and, thus, costs can be reduced because the process of assembling an insulator tube with the field coil is eliminated and, in addition, a defect rate attributable to the simplification of the work process can be minimized because a welding process, a soldering process, a bending process and an epoxy coating process are performed on twisted parts, which are formed on the field coils and the lead wires in the guide pockets of a rotor insulator without interfering with neighboring protrusions.
2. Description of the Related Art
Generally, a vehicle alternator is one of the electrical parts for a vehicle engine. In order to increase the generated voltage at low speed and to maintain stable performance at high speed, a typical three-phase alternator, which is called an ‘alternator,’ is used.
Such a three-phase alternator for vehicles, which is connected to an engine via a belt, enables a rectifier to convert Alternating Current (AC) electricity, which is generated by a stator assembly when a rotor assembly is in an excited state, into Direct Current (DC) electricity, and functions to recharge a discharged battery with power and to supply current, which is necessary to operate other electrical parts, thereto, while supporting various electrical loads on a vehicle.
Here, the rotor assembly is provided with an exciting coil and a slip ring on a shaft in order to form an electromagnetic field caused by exciting current, and receives both the impact and the vibration, which occur due to the traveling of a vehicle, in the state in which it is rotated by the driving force of an engine, and thus the durability thereof is most important.
FIG. 1 is a sectional view showing a conventional vehicle alternator, FIG. 2 is a view showing the rear fan of the conventional vehicle alternator, and FIG. 3 is a view schematically showing the connection structure between the rear fan and a wire in the conventional vehicle alternator.
As shown in FIG. 1, the conventional vehicle alternator 100 is configured such that a stator assembly 114, which includes a stator core 112 and a stator coil 113, is pressed between a front housing 111 and a rear housing 110 and is fitted thereinto. Furthermore, a rotor shaft 116, which is supported by bearings 115, which are pressed and fitted into the front housing 111 and the rear housing 110, is provided inside from the stator assembly 114.
A spool bobbin 119, to which a rotor coil 117 is wound, is pressed and fitted into the middle portion of the rotor shaft 116, and rotor segments 122, having a plurality of rotor poles 120 arranged in the direction of the shaft, are coupled to each other to contain the spool bobbin 119 outside the spool bobbin 119, and thus a rotor assembly 124 is completed.
That is, the rotor assembly 124 includes the rotor coil 117, the rotor segments 122 and the spool bobbin 119, which are disposed around the rotor shaft 116, and a rear fan 130, which is provided in the rear.
Furthermore, a voltage regulator, which is used to maintain the voltage generated from the rotor assembly 124 and the stator assembly 114 constant, and a rectifier 126, which is used to convert AC electricity into DC electricity, are mounted outside the slip ring 118 of the rotor assembly 124.
Furthermore, the Slip Ring End (SRE) of the rotor shaft 116 is located so as to pass through the rear fan 130. One or more coil incoming holes 132 for bringing field coils 117a, which extend from the rotor coil 117, thereinto are formed at proper positions in the rear fan 130.
Here, each of twisted parts 137 is formed by pulling out both a lead wire 118a of the slip ring 118 and a field coil 117a of the rotor coil 117 through the rear fan 130 and then twisting the lead wire 118a and the field coil 117a around each other. Bonding portions 139, which are formed by welding, are formed on the twisted parts 137.
Meanwhile, the rear fan 130 is called a ‘cooling fan.’ The coil incoming holes 132 for bringing the field coil 117a of the rotor coil 117 thereinto are formed in respective proper positions on the rear surface thereof, and coil guide grooves 133 for guiding the respective field coils 117a are formed in respective proper positions on the front surface thereof to have a predetermined length in the central direction of the rear fan 130.
As described above, the lead wires 118a of the slip ring 118, which are bent at the entrance of the coupling hole 131 of the rear fan 130 and are mounted in the front, and the field coils 117a of the rotor coil 117, which are brought into the front of the rear fan 130 through the coil incoming hole 132 and are seated in the respective coil guide grooves 133, are connected to respectively correspond to each other.
In this case, in order to connect the lead wires 118a of the slip ring 118 and the field coils 117a of the rotor coil 117 to respectively correspond to each other, ultrasonic welding is performed after twisting or tig welding.
However, there are problems in that an electrical short circuit may occur in the vehicle alternator 100 due to the impact that is transmitted to the lead wires 118a by the vibration, which occurs due to the ultrasonic welding, which cause a lead wire 118a to be released and to come into contact with the 115, and in that, when the alternator 100 is rotated at high speed during the travel of a vehicle, a defect, such as a short circuit, which occurs in the alternator 100 due to disconnection of the lead wires 118a, may occur.
Furthermore, there is a problem in that it is difficult to manage the quality of a product in an early stage because the structure of fastening the lead wires 118a and the field coils 117a by ultrasonic welding is formed such that whether the lead wires 118a are disconnected cannot be determined from the outside.
Furthermore, parts of the field coils 117a of the rotor coil 117 are exposed outside from the rotor assembly 130, so that oxidation may occur due to corrosion. Each of the field coils 117a has a structure in which the outer surface of a wire, which is a conductor, is surrounded by a plastic insulator tube, which is a nonconductor. In this case, it is difficult to automate the assembly process of covering wires with insulator tubes, and it is also very difficult to assemble a field coil 117a in each insulator tube while maintaining accurate dimensions.
In addition, if movement of the field coils 117a in such insulator tubes is not completely prevented, it may become a potential defect at high speeds. In the case where a soldering process is used to electrically connect the lead wires 118a and the field coils 117a to each other, solder flows into each insulator tube due to the capillary phenomenon in the insulator tube, so that the insulator tube may be hardened or degraded and, in addition, the insulator tube may be degraded when tig welding or ultrasonic welding is performed.